Fix path to KURL.h in FileMetadata.h.

KURL.h has moved to platform/weborigin/.

BUG=

Review URL: https://codereview.chromium.org/111053002

git-svn-id: svn://svn.chromium.org/blink/trunk@163500 bbb929c8-8fbe-4397-9dbb-9b2b20218538